Implement mosaic for BG modes 1, 2, 3 and 4
Implement mosaic for BG modes 1, 2, 3 and 4

matthewbauer/gbajs,JershXL/gbajs,ElliottAYoung/gbajs,JershXL/gbajs,ElliottAYoung/gbajs,matthewbauer/gbajs,endrift/gbajs,endrift/gbajs